First off, you're hunting for an online copywriter. They're the ones who have the requisite experience for writing SEO copy naturally and artfully without compromising the quality of the content. When you're combing through resumes the first thing you want to see is that the candidate has written for the search engines. It's a staple skills these days. While print copywriters can do a decent job, you need the special skill-set of an online writer to take full advantage of the interactive marketplace.
Next you'll be looking for signs of creativity. You know, basic signs of Life - something in their portfolio that tells you, hey, this writer has original ideas and isn't just spinning dead copy over and over again. A good way to scout creativity is to read the headlines and calls-to-action in their portfolio work. Headlines are where copywriters usually get to wax the most bold and creative with their words. Calls-to-action show how well they can write in a tight space. Read them carefully. Does their copy jump off the page? Can they be original without sounding clumsy, awkward, or forced? Can they make you want to read more? And can they do it with brevity? You want your copywriter to have wit AND the killer instinct. It's a fine line. Make them walk it. When you're going through their portfolio, check for a wide array of creative proof including landing pages, banners, splash and squeeze pages, long and short product copy - you know, The Works.
Results come next. You have to know their writing can prove itself through arithmetic. It's not like with other writers. You have to see more than just creativity, spelling, grammar, style and flow. Copywriters have to be able to pump the numbers. So ask for them to share click-through and open rates on some of their creative. Look for consistent above-average performance in those numbers, but also the ability to generate an occasional blockbuster creative. If they have examples of lots of click-throughs around 3%-5%, that's pretty damn sharp. And if they can produce the odd email subject line with a colossal 75% open rate, that's even better and means they've got the potential to write with dynamite.